The NEXT Longitudinal Study of Adolescent Health examines a nationally representative cohort of 2,700 10th-grade students recruited during the 2009-2010 school year from 81 schools (both public and private) with an oversample of African-American students. In 10th grade, participants completed a survey focusing on substance use, obesity-related behaviors, driving, dating violence, and social networks. In addition, anthropometric data (height, weight, and waist circumference) and saliva (genetic material) were collected. Geocodes of home addresses are linked with other databases to provide neighborhood information and a school administrator survey provides information about school environment, programs, and policies. In 11th grade and 12th grades, participants complete the survey on-line or by phone and anthropometric measures are repeated. Substance use was examined at baseline (grade 10). Recent alcohol use was reported by more than one-third (35%) of these adolescents, binge drinking by 27%, and cigarette smoking by 19%. Use of marijuana was most common among illicit drugs (26%), followed by misuse of medication (9%) and use of other illicit drugs (8%). Non-users of drugs reported lower levels of depressive and physical health symptoms, whereas users of multiple drugs reported higher levels of physical health and depressive symptoms. In the year after high school, participants complete the survey on-line or by phone. Using the anthropometric data gathered at the initial assessment, NEXT participants are categorized as overweight or normal weight based on CDC guidelines. A total of 280 overweight and 280 normal weight were randomly selected for participation in NEXT Plus. NEXT Plus participants complete three 24-hour dietary recalls, wear an accelerometer during waking hours to assess physical activity and sedentary behavior for 7 days, wear an actiwatch continuously for 7 days to assess sleep patterns, and complete an activity diary during the same 7-day period. Blood pressure is assessed in addition to repeating the anthropometric measures. Fasting blood samples are collected to assay fasting blood glucose, HbA1c, total cholesterol, triglycerides, LDL-C, HDL, C-reactive protein, uric acid, and cotinine. Participants in NEXT Plus complete a brief survey asking about the prescription or over-the-counter medicines he/she takes on a regular basis and details about the neighborhood where he/she lives. The participants primary caretaker is asked to complete a brief survey about the adolescents chronic illness and medicine use. During the 3rd year of the study, a subsample of participants will be recruited to have their cars instrumented to evaluate driving performance during a 12-month period.